Method and apparatus for delivering power to semiconductors

ABSTRACT

A semiconductor package includes a VLSI semiconductor die and one or more output circuits connected to supply power to the die mounted to a package substrate. The output circuit(s), which include a transformer and rectification circuitry, provide current multiplication at an essentially fixed conversion ratio, K, in the semiconductor package, receiving AC power at a relatively high voltage and delivering DC power at a relatively low voltage to the die. The output circuits may be connected in series or parallel as needed. A driver circuit may be provided outside the semiconductor package for receiving power from a source and driving the transformer in the output circuit(s), preferably with sinusoidal currents. The driver circuit may drive a plurality of output circuits. The semiconductor package may require far fewer interface connections for supplying power to the die.

FIELD OF THE INVENTION

This invention relates to the field of switching power supplies and moreparticularly to power converters that supply power to largesemiconductor devices such as processors and ASICs.

BACKGROUND

Many large scale semiconductors require high current, e.g. 100 A ormore, at low voltages, e.g. 1V, or less, dissipate large amounts ofpower, challenging packaging technologies to accommodate power, thermal,and signal demands. Resonant switching power converters may be used asfixed ratio current multipliers in power conversion systems to providehigh current at a low voltage.

SUMMARY

In one aspect, in general, a method of supplying power received from aninput source at an input voltage to circuitry on one or moresemiconductor chips mounted in a semiconductor package at a DC outputvoltage is provided. The method includes providing a driver circuit fordeployment outside the semiconductor package having an input forreceiving power from the source, circuitry adapted to drive atransformer, and a driver output; providing one or more output circuitsfor deployment in the semiconductor package, each output circuitincluding a printed circuit board, a power transformer including a firstwinding and a second winding, an input connected to the first windingfor receiving AC power from the driver output, a rectification circuitconnected to the second winding for rectifying power received from thetransformer, and an output connected to the rectification circuit forsupplying DC power to the one or more semiconductor chips; providing apower bus for carrying AC power from the driver output to the input ofeach of the one or more output circuits in the semiconductor package;operating the driver circuit to drive the transformer in a series ofconverter operating cycles, each converter operating cycle characterizedby two power transfer phases of essentially equal duration during whichone or more switches in the driver circuit are ON and power istransferred from the input to the output via the transformer; anddeploying the driver circuit at a first location outside of thesemiconductor package. Power is supplied to the semiconductor package bythe driver circuit at a bus voltage that is a multiple, X, times greaterthan a load voltage required by the one or more semiconductor chips.

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; one or more output circuits housed in the semiconductor package,each output circuit including a printed circuit board, a powertransformer including a first winding and a second winding, an inputconnected to the first winding for receiving AC power, a rectificationcircuit connected to the second winding for rectifying power receivedfrom the transformer, and an output connected to the rectificationcircuit for supplying DC power to the one or more semiconductor chips;and a power bus connected to selected interface connections for carryingAC power at a bus voltage from the system board to the input of each ofthe one or more output circuits in the semiconductor package. The busvoltage is a multiple, X, times greater than a voltage required by theone or more semiconductor chips.

In another aspect, in general, a method of packaging a semiconductor dieincludes providing a substrate for mounting to a bottom surface of thesemiconductor die; providing a lid to extract heat from a top surface ofthe semiconductor die; providing one or more output circuits having abottom surface mounted to the substrate for supplying power to thesemiconductor die; and conducting heat from the bottom of thesemiconductor die, into the substrate, from the substrate into thebottom of the one or more output circuits, out of the top of the one ormore output circuits, into the lid.

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; and one or more power conversion circuits housed in thesemiconductor package, each power conversion circuit including aninductive component for converting power from an input at an inputvoltage to an output at an output voltage for delivery to the one ormore semiconductor chips, the inductive component having a magneticallypermeable core having an effective permeability of at least 25. Theratio of input voltage to output voltage is fixed, subject to a seriesresistance, and is at least 5.

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; and one or more power conversion circuits housed in thesemiconductor package, each power conversion circuit including at leastone switch, a switch controller, and an inductive component forconverting power from an input at an input voltage to an output at anoutput voltage for delivery to the one or more semiconductor chips,wherein the switch controller is configured to turn the at least oneswitch ON or OFF at essentially zero voltage. The power conversioncircuit ratio of input voltage to output voltage is fixed, subject to aseries resistance, and is at least 5.

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; and one or more power conversion circuits housed in thesemiconductor package, each power conversion circuit including at leastone switch, a switch controller, and an inductive component forconverting power from an input at an input voltage to an output at anoutput voltage for delivery to the one or more semiconductor chips,wherein the switch controller is configured to turn the at least oneswitch ON or OFF at essentially zero current. The power conversioncircuit ratio of input voltage to output voltage is fixed, subject to aseries resistance, and is at least 5.

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; and one or more power conversion circuits housed in thesemiconductor package, each power conversion circuit including at leastone switch, a switch controller, and an inductive component forconverting power from an input at an input voltage to an output at anoutput voltage for delivery to the one or more semiconductor chips. Theswitch controller is configured to operate the at least one switch tolimit slew rates of voltage in the converter to 5 (Vpeak/Top).

In another aspect, in general, an apparatus includes a semiconductorpackage including a substrate having a plurality of interfaceconnections connected to at least one surface of the package substrateand one or more semiconductor chips mounted to the substrate, theinterface connections adapted for electrical connection to a systemboard; and one or more power conversion circuits housed in thesemiconductor package, each power conversion circuit including at leastone switch, a switch controller, and an inductive component forconverting power from an input at an input voltage to an output at anoutput voltage for delivery to the one or more semiconductor chips. Theswitch controller is configured to operate the at least one switch tolimit slew rates of current in the converter to less than or equal to5*(Ipeak/Top).

In another aspect, in general, a method of supplying power received froman input source at an input voltage to circuitry on one or moresemiconductor chips mounted in a semiconductor package at a DC outputvoltage is provided. The method includes providing one or more outputcircuits for deployment at one or more locations near or adjacent to thesemiconductor package, each output circuit including a printed circuitboard, a power transformer including a first winding and a secondwinding, an input connected to the first winding for receiving AC power,a rectification circuit connected to the second winding for rectifyingpower received from the transformer, and an output connected to therectification circuit for supplying DC power to the one or moresemiconductor chips; providing a driver circuit for deployment at alocation spaced apart from the one or more output circuits, the drivercircuit having an input for receiving power from the source, circuitryconfigured to drive a transformer, a driver output for supplying ACpower to the one or more output circuits, and circuitry configured tocontrol the power supplied to the one or more output circuits; providinga power bus for carrying AC power from the driver output to the input ofeach of the one or more output circuits; operating the driver circuit todrive the transformer in a series of converter operating cycles, eachconverter operating cycle characterized by two power transfer phases ofessentially equal duration during which one or more switches in thedriver circuit are ON and power is transferred from the input to theoutput via the transformer; and deploying the driver circuit at a firstlocation outside of an area immediately near or adjacent to the one ormore output circuits. Power is supplied to the one or more outputcircuits by the driver circuit at a bus voltage that is a multiple, X,times greater than the load voltage required by the one or moresemiconductor chips.

In another aspect, in general, a method of supplying power received froman input source at an input voltage to a load at a DC output voltage isprovided. The method includes providing one or more current multipliermodules at one or more locations in close proximity to the load, the oneor more current multiplier modules having a transformer and circuitryfor supply DC power to the load; and providing a driver module at alocation spaced apart from the one or more current multiplier modules,the driver module having circuitry including an input for receivingpower form the input source, control circuitry for generating acontrolled driver voltage, and driver circuitry for generating AC powerfor driving the transformer in each of the one or more currentmultiplier modules.

In another aspect, in general, a method of making a planar magneticcomponent is provided. The method includes providing a multilayerprinted circuit board (PCB) including conductive features arranged onconductive layers of the PCB to form one or more windings around one ormore predetermined axes; forming a hole in the PCB at each of the one ormore predetermined axes to accommodate one or more core legs, whereinfor each hole, an inner edge of one of the windings overlaps an edge ofthe hole in a lateral direction after the hole is formed; assembling afirst magnetically permeable plate to a first surface of the PCBcovering a selected one or more of the holes at the one or morepredetermined axes; assembling a second magnetically permeable plate toa second surface of the PCB covering the selected one or more of theholes at the one or more predetermined axes; filling the selected one ormore of the holes with at least one of a magnetically permeable fluid orpowder; and sealing the selected one or more holes to prevent the atleast one of magnetically permeable fluid or powder from escaping.

In another aspect, in general, an apparatus includes a planar magneticstructure including a multilayer printed circuit board (PCB) having afirst surface, a second surface, and conductive features arranged onconductive layers of the PCB to form one or more windings around one ormore predetermined axes; a hole in the PCB at each of the one or morepredetermined axes, each hole having an inner edge aligned with an innercircumference of one of the windings; a first magnetically permeablesection affixed to the first surface of the PCB covering a selected oneor more of the holes; a second magnetically permeable section affixed tothe second surface of the PCB covering the selected one or more of theholes; and at least one of a magnetically permeable fluid or powderdisposed in the selected one or more of the holes. The at least onemagnetically permeable fluid or powder is contained within the selectedone or more holes.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 shows an isometric view of a semiconductor package withintegrated power-converter output circuitry.

FIG. 2 shows a top plan view of the semiconductor package.

FIG. 3 shows a side view of the semiconductor package.

FIG. 4 shows a cross-sectional view of a portion of the substrate of thesemiconductor package revealing power input connections for the outputcircuitry.

FIG. 5 shows a schematic drawing of a first modular power converterbased on the SAC topology.

FIG. 6 shows a schematic drawing of a second modular power converterbased on the SAC topology.

FIG. 7 shows a schematic drawing of a system including a third modularpower converter with multiple output chips integrated into asemiconductor package to supply power to a large semiconductor die.

FIG. 8 shows an isometric view of an output circuit.

FIG. 9 shows a schematic block diagram of a system including a fourthmodular power converter including an improved driver circuit.

FIG. 10 shows an isometric view of the semiconductor package with thelid exploded from the assembly.

FIG. 11 shows heat flow in a side view of the semiconductor package withlid.

FIG. 12 shows an exploded view of a transformer structure for use in anoutput circuit.

FIG. 13 shows a schematic block diagram of a system including a fifthmodular power converter.

FIG. 14A and FIG. 14B show exploded and assembled views of an alternatetransformer structure for use in an output circuit.

FIG. 15A and FIG. 15B show exploded bottom and top isometric views of asecond semiconductor package.

FIG. 16A and FIG. 16B show top and bottom isometric views of the secondsemiconductor package assembled.

FIG. 17 is a side view of the second semiconductor package.

FIG. 18 is a bottom isometric view of a third semiconductor package.

FIG. 19 is a schematic drawing of a system including a sixth modularpower converter with an output chip integrated into a semiconductorpackage to supply power to a large semiconductor die.

FIG. 20A and FIG. 20B show first and second mounting positions for thesecond and third semiconductor packages.

Like references symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

In contemporary electronic systems, space is at a premium on customercircuit boards, e.g. on a circuit board near a processor. Additionally,thermal management considerations place limits on the efficiency andpower dissipation of power supplies at, or near, the point of load. Manyvery large scale integrated (“VLSI”) semiconductor dies such as centralprocessing units (“CPU”), graphics processing units (“GPU”), andapplication specific integrated circuits (“ASIC”) are mounted to amultilayer ceramic substrate which translates the electrical connectionsfrom the die to larger connections suitable for interfacing with acustomer motherboard. As feature sizes decrease and transistor countsincrease, so too do the power supply current requirements for such largechips. Current requirements for a typical CPU can easily exceed 200 ampscreating challenges for the package and system designers to efficientlysupply such high currents. For example, power connections between thecomponent package (such as a chip carrier or substrate or other packagein or on which the semiconductor die is mounted) and the printed circuitboard (PCB) on which the package is mounted may demand a large number ofconnector pins, leads, solder bumps, etc., to carry very high currentschallenging package designers to accommodate both power and signalrequirements. In many cases the large number and high frequency demandsof signals may limit the maximum voltage, e.g. the interlayer breakdownvoltage, to which the substrate or package may be subjected, in somecases as low as a few volts, further challenging power connections toand within the package or substrate.

A Factorized Power Architecture well suited for supplying power to lowvoltage high current loads is described in Vinciarelli, Factorized Powerwith Point of Load Sine Amplitude Converters, U.S. Pat. No. 6,975,098,issued Dec. 13, 2005 (the “Micro FPA Patent”) and U.S. Pat. No.6,984,965, issued Jan. 10, 2006 (the “FPA Patent”) (both assigned toVLT, Inc. of Sunnyvale, Calif., and the entire disclosure of each patentis incorporated herein by reference). Power converters which function asDC-to-DC transformers called Voltage Transformation Modules (“VTM”) andSine Amplitude Converters (“SAC”) which have a transfer functionapproximating Vo=K_(VTM)*Vin−Io*R_(VTM) are described in Vinciarelli,Factorized Power with Point of Load Sine Amplitude Converters, U.S. Pat.No. 6,930,893, issued Aug. 16, 2005 (the “SAC Patent”) and inVinciarelli, Point of Load Sine Amplitude Converters and Methods, U.S.Pat. No. 7,145,786, issued Dec. 5, 2006 (the “POL SAC Patent”) (bothassigned to VLT, Inc. of Sunnyvale, Calif., the entire disclosure ofeach patent is incorporated herein by reference).

I. In-Package Power Conversion Topologies

A. Fault-Tolerant Topology

FIG. 5 is a replica of FIG. 14 from U.S. Pat. No. 9,112,422, issued Aug.18, 2015, which is incorporated herein by reference in its entirety(hereinafter the “FT Patent”). In FIG. 5, a power converter 400 is shownincluding a driver 420 connected to drive one or more point-of-load(“POL”) current multiplier circuits 430 having inputs 447, 448 connectedto the driver outputs 427, 428 via an AC power bus 410. The driver 420may comprise a full-bridge fault-tolerant input circuit such as inputcircuit 250 of FIG. 11 in the FT Patent and a switch controller 425similar to the switch controller described in connection with FIG. 11 ofthe FT Patent.

The POL circuit 430 may include a transformer circuit 440 and arectification circuit 450. The transformer circuit 440 may include none,one, or both, of resonant capacitors 441, 442 shown in FIG. 5 connectedto the primary winding 82 of transformer 81. The secondary winding maybe connected to a full-bridge fault-tolerant rectification circuit 450as shown in FIG. 5 and described in the FT Patent. The full-bridgefault-tolerant rectification circuit 450 may use switches, R1, R2, R3,R4, operated as rectifiers in the manner described in the FT Patent inconnection with output circuit 100 of FIG. 3 (of the FT Patent) and maypreferably employ the common-source synchronous rectifiers described inconnection with FIGS. 7 and 8 (of the FT Patent). Note that a simplifiedsymbol is used in FIG. 5 for switches S1-S4 and R1-R4 (instead of theenhancement mode MOSFET symbols used, e.g. in FIGS. 2-4, 7, 8, 11 of theFT Patent) in which the arrow indicates the direction of current flowthrough the intrinsic body drain diode when the switch is open.

As its name implies, the POL circuit 430 (FIG. 5) may be designed to bedeployed as close to the point of load, where space and thermalrequirements are stringent, as possible. Because the driver circuit 420does not need to be close to the point of load, it may be deployedelsewhere, away from the point of load, reducing the space required bythe POL circuitry and reducing the power dissipation in proximity to theload. One benefit of removing the driver circuitry from the POL is thata larger transformer structure and array of output switches (R1-R4) maybe used in the POL circuit thereby improving overall converterefficiency and further reducing dissipation at the POL. Similarly,larger input switches (S1-S4) may be used in the driver circuit tofurther improve overall efficiency without impacting spaceconsiderations at the POL.

However counter intuitive separating the driver 420 from the POLcircuitry 430 and deploying an AC bus may initially seem, closerinspection refutes such objections. For example, power carried by the ACbus 410 may be spectrally pure (sine wave) and voltage and current slewrates substantially lower than those typically found in other switchingpower converter topologies, such as buck and multiphase buck converters,and even in the signal paths of computer circuitry, reducing concernsabout noise and electromagnetic emissions.

The POL circuit 430 may be enclosed as a single module, i.e. packagedfor deployment as a single self-contained unit (as shown in FIGS. 5, 6,and 8), or as a multiplicity, specifically a pair, of modules fordeployment as component pairs, e.g. 440 and 450, (as shown in FIGS. 1-3,7). Because switches R1-R4, need only withstand the output voltage, therectification circuit 450 may be integrated (with or without the controlcircuitry, e.g. as shown in FIGS. 7 and 8 of the FT Patent) onto a diewith circuitry to which it supplies power, e.g. a processor core or anASIC.

B. Alternative POL Topology

Referring to FIG. 6, an alternate embodiment 401 of the convertertopology is shown comprising driver circuit 481 and POL circuit 431. Inaddition to outputs 427, 428 for driving the AC power bus 410, thedriver circuit 481 as shown also includes a bias output 429 forsupplying a small amount of power to operate control circuitry in thePOL, and a control output 426 for supplying timing and/or controlinformation to the POL circuit 431. A small signal bus 415 may beprovided to connect driver outputs 429, 426, which may be low power andlow voltage signals, to the input of the POL circuit 431.

An example of suitable control circuitry is described in Digital Controlof Resonant Power Converters, Vinciarelli et al., U.S. Pat. No.9,166,481, issued Oct. 15, 2015, assigned to VLT, Inc. and incorporatedhere by reference (the “Controller patent”), e.g. in connection withFIGS. 15 and 16. The driver may further include clamp and controlcircuitry to implement the clamped capacitor techniques to increaseefficiency as described in Clamped Capacitor Resonant Power Converter,Vinciarelli, U.S. patent application Ser. No. 14/874,054, filed Oct. 2,2015 (the “CSAC” patent application), assigned to VLT, Inc. andincorporated here by reference. As shown in FIG. 6, the converter 401may be partitioned with the resonant capacitors 441, 442 located in thedriver module 481. Alternatively, a single resonant capacitor may belocated within the driver for ease of implementing the clamp circuitry.

The POL circuit 431 as shown may include a switch driver 460 havinginputs 449, 446 for receiving a bias voltage (449) and a control signal(446) from the driver circuit 481. The bias voltage provides power tooperate the switch driver and the control signal provides timinginformation to the switch driver to synchronize operation of thesecondary switches 451, 452, 453, 454 as controlled rectifiers. Thesecondary controller 200B shown in FIG. 15 of the Controller patent maybe used for the POL switch driver 460 in FIG. 6. Although the switchdriver 460 is shown in FIG. 6 with a dedicated bias supply from thedriver, it may, as shown in the Controller patent, derive the power itrequires to operate from the control signal or from an independent biassupply. The switch driver 460 may alternatively be co-packaged with, orintegrated within, the driver circuit 481 and the secondary switches maybe driven directly by the driver circuit 481, in which case the smallsignal bus may be used to carry gate drive signals for the secondaryswitches instead of the bias and timing/control signals shown.

The POL circuit 431 may be enclosed as a single module, i.e. packagedfor deployment as a single self-contained unit, or as a plurality ofmodules for deployment as component parts, e.g. transformer module 440,secondary switches 451-454, and driver circuit 460. Because thesecondary switches 451-454 need only withstand the output voltage, therectification circuit 450 may be integrated with driver circuitry 460onto a single die or even on the same die as the circuitry to which itsupplies power, e.g. a processor core, such as a GPU, CPU, or ASIC.

C. Single-Driver Multi-POL Topology

Referring to FIG. 7, another embodiment of the topology is shown asconverter 402 including a single driver circuit 481 and a plurality ofPOL circuits, 431-1, 431-2. The driver circuit 481 and POL circuits431-1, 431-2 may be the same as driver circuit 481 and POL circuit 431shown in FIG. 6, respectively. The converter 402 may include an AC bus410 connected to outputs 427, 428 of driver circuit 481 and a smallsignal bus 415 (low power, low voltage) connected to the bias 429 andcontrol 426 outputs of the driver 481 for establishing the requisiteconnections to each POL circuit 431-1, 431-2.

The POL circuits may be connected to operate with their outputs 413, 414connected in parallel for low voltage loads such as a CPU, GPU, or ASIC101. Alternatively, inputs to the POL circuits may be connected inseries for lower output voltages. To summarize, power may be supplied tothe POL circuits 431 by the driver 481 at a bus voltage, Vbus, that is amultiple, X, times greater than the voltage, Vload, required by the load(e.g., one or more semiconductor chips 101). The multiple X maypreferably be an integer (or alternatively a non-integer rationalnumber), preferably at least 5, or greater, e.g., 10, 20, and morepreferably 40 or more. Each POL circuit may have a fixed voltagetransformation ratio, K=Vout/Vin at a load current, where K may be equalto or greater than the turns ratio or step-down ratio, N, of therespective transformer in each POL circuit, depending for example on theoutput circuitry. The voltage transformation ratio, K, of each POLcircuit may be less than or equal to the inverse of the multiple,X=Vbus/Vload, depending on the number and configuration of POL circuitssupplying the load. For example, with the inputs and outputs of two ormore POL circuits connected in parallel, the bus voltage, Vbus, may beset to X=1/K times the load voltage, Vload: Vbus=Vload/K. Alternatively,it may be preferable for very low output voltages, to arrange a number,M, of POL circuits with their respective inputs connected in series andoutputs connected in parallel, in which case the bus voltage Vbus may beset to X=1/(M*K) times the load voltage, Vload: Vbus=Vload/(M*K). ThePOL circuits 431-1, 431-2 may be deployed as close as possible to theload or preferably co-packaged together with the load as shownschematically in FIG. 7 and mechanically in FIGS. 1-3.

D. Integrated Driver Regulator

Referring to FIG. 9, another power converter system 403 is shownincluding a driver 490 electrically connected to the semiconductorpackage 100 via connections formed by a system PCB in which the driver490 and semiconductor package 100 may be mounted. The bias and controlconnections (415, FIG. 6) and AC power connections (410, FIG. 6) betweenthe driver 490 and the substrate 102 are not shown in FIG. 9 forclarity, however, it should be understood that the desired connections,e.g. as shown in FIGS. 5-7 may be provided in the manner describedabove. The driver 490 as shown in FIG. 9 may include the transformerdriver circuitry 481 (which may be of the type shown in FIG. 5 or 7), apower regulator circuit 482, and a supervisory circuit 483. The powerregulator 482 may be used to control the voltage, VF, input to thedriver circuit 481 as a means of controlling the AC voltage supplied tothe POL circuits 431-1, 431-2 and in turn the DC output voltage to thesemiconductor die 101.

The supervisory circuit 483 may be connected to communicate with thesemiconductor die 101 and optionally the POL circuits 431-1, 431-2 via adigital or analog communication bus 497 as shown in FIG. 9. Althoughshown as a single bus, the semiconductor die 101 and POL circuits 431may have one or more separate buses for direct communication on thesubstrate 102 and the supervisory circuit 483 may have separate bussesfor communication with the die 101 and with the POL circuits 431, e.g.to accommodate different communication speeds and protocols. Thesupervisory circuit 483 may be connected to communicate with externalsystem components via a digital or analog communication bus 495 as shownin FIG. 9, e.g. to report on conditions in the semiconductor package orpower system, e.g. temperature, voltage, current, power, faultconditions, etc. or to receive commands, e.g. reset, disable, etc. Forexample, some CPU's require the power system to adjust the voltagesupplied to the CPU in response to commands issued by the CPU, e.g. manyIntel processors send VID information to a voltage regulator which inturn adjusts the voltage supplied to the processor. The supervisorycircuit 483 may receive such voltage commands from the semiconductor die101 via bus 497 and issue appropriate commands to regulator 482 viadigital or analog communication bus 496 to adjust the output voltage.The regulator may, in response to commands received from the supervisorycircuit 483, adjust the DC output voltage of the output circuits (viathe control voltage, VF) to comply with the requirements of thesemiconductor die 101.

E. Multi-Driver Multi-Rail Topology

Referring to FIG. 13, another embodiment of the topology is shown asconverter 404, which is configured to supply multiple voltage supplyrails, V1, V2, to the semiconductor load 101. Converter 404 includes twodriver circuits 490-1, 490-2 for driving two POL circuits, 431-1 and431-2, respectively. The driver circuits 490-1, 490-2 and POL circuits431-1, 431-2, may be of the same type as driver circuit 490 (shown inFIG. 9) and POL circuits 431 (shown in FIG. 6), respectively. Forsimplicity, the connections between the drivers and POL circuits andsemiconductor package are shown as single connections, it beingunderstood that each may include an AC power bus, a control bus, andcommunications bus as described above. Preferably, the drivers may besynchronized to the same clock as shown in FIG. 13 by the broken arrowfrom driver 490-1 (the master) to driver 490-2 (slave). Preferably, thePOL circuits 431-1 and 431-2 may be co-packaged as a single POL circuitmodule 431. Each driver may, in response to commands received from thesemiconductor die 101, adjust the DC output voltage of the POL circuitassociated with it to comply with the requirements of the semiconductordie 101. For example, driver 490-1 may adjust the output V1 of POLcircuit 431-1 and driver 490-2 may adjust the output V2 of POL circuit431-2.

F. Driver Compensation

Separation of the driver 481 and integrated controller 425 (FIG. 6) fromthe POL circuits 431 may introduce parasitic capacitances andinductances, which, depending upon the layout of the customer's systemboard, e.g. the distance between driver and POL circuits and the sizeand routing of the electrical connections between them, may adverselyaffect operation of the converter. For example, the parasitic inductancemay lower (raise) the resonant frequency (period) of the resonantcircuit (formed by the resonant capacitors 441, 442 and the transformer440) which if uncompensated can lead to timing errors in the operationof the switches disrupting zero-voltage switching (ZVS) and zero-currentswitching (ZCS) operation, which in turn may lead to increased losses,power dissipation, and noise.

Preferably, the driver 481 may include compensation circuitry able todetect and adjust for the effects of parasitic capacitances andinductances introduced by the separation of driver and POL circuits andthe vagaries of different system board layouts on converter operation.One method uses current detection, e.g. in one or more of the primaryswitches (e.g. switches 421, 422, 423, 424 in FIG. 6) of the drivercircuit (using known techniques such as sensing the voltage across aswitch while in the ON state) to detect errors in the switch timing. Forexample, if the compensation circuitry detects that the resonant currentat the end of a power transfer interval has not returned to zero, thecontroller may incrementally increase the duration of the power transferintervals until the current returns to zero or within a tolerance bandof zero, e.g. 1% of the maximum resonant current. For the clampedversion described in the CSAC patent application, the compensationcircuitry may additionally sense the rate of change of the switchcurrent at the end of the first resonant interval, extending it untilthe rate of change of the current returns to zero, or within a toleranceband of zero, or within a percentage of the maximum rate of change, e.g.10%, 5%, or 1%. In this way, the compensation circuitry may adjust theoverall timing of the converter operating cycle and/or specific aspectsof the converter operating cycle, e.g. the power transfer intervals(described in the SAC, POL-SAC, and Controller patents), or the firstand second resonant intervals (described in the CSAC patentapplication), etc.

II. Semiconductor Package with Top-Mounted Integrated POL Circuits

In FIGS. 1, 2 and 3, a semiconductor package 100 is shown (in isometric,top plan, and side views, respectively) including a multilayer substrate102, a large semiconductor die 101, such as an ASIC, CPU, or GPU, and aplurality of POL modules 110-1, 110-2 mounted to the substrate adjacentto the semiconductor die 101. As shown in FIG. 8, the POL modules 110may be packaged as a leadless module, such as described in Vinciarelli,et al., Panel Molded Electronic Assemblies with Multi-Surface ConductiveContacts, Application Ser. No. 14/731,287, filed Jun. 4, 2015, andincorporated here by reference (the “Panel Mold” application”), havingconnections 115 (FIGS. 1, 8) for surface mount soldering to respectiveconductive pads on the substrate 102 and preferably include shieldingfor improved low noise performance. (See, e.g. leadless electronicmodule 100 described in connection with FIGS. 1-3 of the Panel Moldapplication.) The POL modules 110-1 and 110-2 (FIGS. 1-3) may eachinclude a respective POL circuit, e.g. 431-1, 431-2, as described inconnection with FIG. 7.

Referring to FIG. 1, the POL modules 110-1, 110-2 are shown having amultiplicity of electrical contacts 115 arranged along their respectiveperimeters. The contacts may be formed as shown in FIGS. 1-3 and 8 (andas described in the Panel Mold application) to extend along the entirevertical span of the perimeter walls and onto the top and bottom modulesurfaces. The common terminals may be extended as shown onto the top andbottom surfaces to form shielding. As shown for the two POL Moduleexample in FIGS. 1-3, a plurality of discrete components 105, such ascapacitors, e.g. for filtering, may be provided in the free space alongthe semiconductor die 101. It may be preferable for very high currentapplications to use four POL modules, each mounted along a respectiveone of the four sides of the semiconductor die 101 to lower theinterconnection resistance between the POL module outputs and the die.Using four POL modules to power the die may allow a reduction in thelength of each POL module, e.g. by a factor of two, leaving space fordiscrete components such as capacitors along a respective one of thefour sides of the semiconductor die 101.

In FIG. 2, several of the contacts 115 are labeled to show theirpreferred function. For example, at the left end of each POL module asshown in FIG. 2, two terminals are labeled consistent with FIG. 7showing the AC power inputs 447-1 and 448-1 for module 110-1 and 447-2and 448-2 for module 110-2; similarly, two terminals are labeled showingthe respective bias and control inputs: 449-1 and 446-1 for POL module110-1 and 449-2 and 446-2 for POL module 110-2. A multiplicity of outputterminals 413-1, 413-2 and ground terminals 414-1, 414-2 are providedalong the perimeter of the POL modules 110-1, 110-2 respectively toprovide a low impedance distributed connection to the substrate.

In FIG. 7, the substrate 102 of semiconductor package 101 is representedwith broken lines: electrical connections between the substrate 102 anda system board (to which it may be connected) are represented byinterface connections 465, 466, 467-1, 468-1, 467-2, and 468-2;connections contained within the broken lines may be formed by thesubstrate 102; and connections outside the broken lines may be formed bythe system board which typically may be a multi-layer printed circuitboard (“PCB”). The driver circuit 481 may be mounted away from thepoint-of-load, e.g. the semiconductor die 101 or the semiconductorpackage 100, on the system level board, which may provide electricalconnections between the driver and the semiconductor package 100 orsubstrate 102 as shown symbolically in FIG. 7. Note that connections tothe semiconductor die 101, which may be great in number, are not shownin FIG. 7 for clarity.

The substrate 102, in typical applications, carries a multitude ofelectrical connections between the semiconductor die 101 and asystem-level PCB using, e.g. connector pins, ball grid array, land gridarray, or other connection schemes. The breakdown voltage of thesubstrate 102 may be very low, e.g. on the order of 3 to 5 volts; thenumber of interface connections available for power connections betweenthe substrate 102 and the system PCB may be limited due to the largenumber of input/output signals (“I/Os”) required by the semiconductordie 101; and consequently the ability to efficiently conduct large powersupply currents may be limited. In FIG. 7, the POL circuit bias powerconnections 449-1 and 449-2 and control connections 446-1 and 446-2 areshown connected to bias and control interface connections 465, 466respectively. The POL circuit power connections 447-1, 447-2, 448-1, and448-2 are shown connected to a power interface connections 467-1, 467-2,468-1, 468-2.

As shown, the bias and control signals (FIG. 7), which are relativelylow in voltage and power, may be handled by the substrate 102 andinterface connections 465, 466 in the same manner as normal I/O signalsto, and within, the package, e.g. the bias and control signals may berouted laterally along the substrate as shown by the small signal bus415 within the substrate 102 (FIG. 7). However, connections to the ACpower bus 410, which may need to carry voltages exceeding the voltagecapabilities of the substrate 102, may not be suitable for wiring on thesubstrate. Accordingly, FIG. 7 shows a separate set of interfaceconnections (467, 468) for carrying AC power from the bus 410 to each ofthe POL circuits (431-1, 431-2): interface connections 467-1 and 468-1for POL circuit 431-1; and interface connections 467-2 and 468-2 for POLcircuit 431-2. The AC power interface connections 467 and 468 will bedescribed in greater detail with reference to the semiconductor packagedrawings of FIGS. 1-4.

A. High Voltage Connections

The section taken along lines 4-4 (FIG. 2) is shown enlarged in thecross-sectional view of FIG. 4 providing physical detail of the AC powerbus 410-2 (FIGS. 4, 7) in the substrate 102. Because its voltage mayexceed the voltage rating of the substrate, the AC power bus, e.g.410-2, may be kept as short as possible in the substrate preferablyextending vertically through the thickness of the substrate 102 from theinterface connections 467-2, 468-2 on the bottom of the substrate to theconductive pads 117-2, 118-2 on top of the substrate for mating with POLmodule terminals 447-2, 448-2, respectively. The interface connections(e.g., 467-2, 468-2) on the bottom of the substrate 102 may beelectrically coupled to connectors on the system board using, e.g.connector pins, ball grid array, land grid array, or other connectionschemes. All lateral travel of the AC power bus in the substrate ispreferably eliminated or, if unavoidable, then minimalized. In theexample shown in FIGS. 1-4, the AC power bus is divided into twosections 410-1 and 410-2 each of which consist of a pair of platedvertical through holes in the substrate 102 around which a minimum keepout distance is maintained to account for the low interlayer breakdownvoltage of the substrate. Thus as shown in FIG. 4, AC power bus 410-2includes two vertical conductive through holes (collectively 410-2)connected to interface contacts 467-2, 468-2 on the bottom of thesubstrate 102 and conductive pads 117-2, 118-2 on the top of thesubstrate 102, all of which are preferably vertically aligned minimizingor eliminating any lateral conduction requirements for the AC power bus.The heavy broken lines 103 in FIG. 4 indicate a volume 104 of thesubstrate 102 defined by a projection around the high voltage connectionin which no other electrical features should be formed to manage therelatively high voltage requirements of the AC power bus and the lowbreakdown voltage of the substrate. Ground referenced through holes maybe formed in the substrate around the keep-out area to provideshielding.

B. Magnetic Field Management

Referring to FIG. 12, an example of a magnetically permeable corestructure 150 in the POL modules 110-1, 110-2 is shown including amultilayer printed circuit board 151 in which the transformer windings(not shown) may be formed around a plurality of holes 155. Thetransformer may incorporate self-aligned windings as described inVinciarelli, Self-Aligned Planar Magnetic Structure and Method, U.S.patent application Ser. No. 14/822,561, filed Aug. 10, 2015, (the“Self-Aligned” patent application) assigned to VLT, Inc. of Sunnyvale,Calif., the entire disclosure of which is incorporated herein byreference). Core legs 154 may be placed in the holes 155 and mated withtop and bottom core plates 152 and 153 when assembled to form completemagnetic loops. A small gap of 1 mil or less may be provided between oneor both of the top and bottom core plates and the legs. Preferably, theeffective magnetic permeability (μ) of the core legs and core plates isgreater than 25 and preferably greater than 100, and more preferablygreater than 200 to contain the magnetic flux during operation. Lowereffective permeability core structures may result in greater fluxleakage which can couple to signal conductors in the substrate,semiconductor die, or system board creating noise problems.

Referring to FIGS. 14A and 14B, an alternate transformer structure 160is shown having essentially the same PCB 151 in which the transformerwindings (not shown), preferably self-aligned windings described in theSelf-Aligned patent application, may be formed around a plurality ofholes 155 to accommodate core legs such as the core legs 154 shown inFIG. 12, and bottom core plates 153 on the bottom surface of the PCB151. The top core plates 162 may as shown include apertures 166 arrangedto align with apertures 155 in the PCB when the core is in position. Thetransformer 160 may be fabricated by affixing the bottom core plates 153to the bottom surface of the PCB 151 with a suitable adhesive such asepoxy. The top core plates 162 may be similarly affixed to the topsurface of the PCB 151 with apertures 166 aligned with apertures 155. Amagnetically permeable fluid, such as a powder with or without asuitable binder material or other injectable material, preferably havinga permeability of 10 or greater, may be injected through apertures 166to fill the PCB apertures 155 and alternatively some or all of the coreapertures 166. After the apertures are filled with the magneticallypermeable material, the core apertures may be sealed with an epoxy orother suitable material to prevent the magnetically permeable materialfrom escaping. One or more plugs can be disposed in one or more of theapertures 166, in which the one or more plugs form seals covering therespective one or more of the apertures 166. Optionally, the PCB may beheated before the apertures are filled and sealed to ensure that theapertures are completely filled after the PCB is cooled. For example,the core plate 153 can be a ferrite core plate, and the core plate 162can be a ferrite core plate having one or more apertures that is/arefilled with one or more plugs.

The transformer structure 160 of FIGS. 14A and 14B may be particularlywell suited to low voltage and high frequency applications such as thePOL circuits discussed above. Using a material that may be injected as apowder or fluid into the apertures in the PCB overcomes the mechanicaltolerances of conventional planar magnetic core structures where smallsolid core legs have to fit within small PCB apertures. By replacingsmall solid magnetic core legs with magnetic powder or fluid, PCBapertures can be filled with a permeable medium providing greater PCBaperture utilization and converter efficiency.

Additionally, as mentioned above, the output circuit may be covered witha conductive covering, preferably connected to a common terminal, toprovide additional shielding.

C. Noise Management

The POL modules 110-1, 110-2, and preferably the driver circuits also,may use zero-current switching and/or zero-voltage switching to minimizethe slew rate of voltages and currents in and around the semiconductorpackage 100 and system board. The power converter topologies shown inFIGS. 6, 7, and 9 may preferably be based on the Sine AmplitudeConverter (“SAC”) topology described in the SAC patent or on the clampedcapacitor resonant topology described in the CSAC patent application.The SAC topology is preferred for the sinusoidal current and voltagewaveforms and zero-current switching (“ZCS”) and zero-voltage switching(“ZVS”) and the ability to constrain the slew rates of voltages andcurrents in the converter. For example, the slew rates may be limited todV/dT≤Vpk/(Top*0.2) and dI/dT≤Ipk/(Top*0.2) in the output circuits shownin FIGS. 6 and 7 using the SAC topology. In contrast, multiphase buckregulators typically exhibit characteristic current slew rates an orderof magnitude greater than those in the output circuits.

In one example, the POL modules 110-1, 110-2 in the semiconductorpackage 100 may use a current multiplication factor K of 48 and an inputvoltage of 48 volts to supply 1 VDC at 100 A to the semiconductor die.Using a SAC topology operating at 1 MHz (Top=1 μS), the maximum voltageis 48V and the maximum current Iin=100/48=2.1 Amps. Thus, the voltageand current slew rates for the output circuit may be limited to 240 V/μSand 10.4 A/μS.

D. Thermal Management

The semiconductor package 100 may include a lid 103, preferably made ofthermally conductive material such as aluminum, copper, or othermetallic or non-metallic thermally conductive material as shown in FIG.10. The lid as shown may have a stepped lower surface to mate oraccommodate the difference in height between the relatively shortsemiconductor die 101 and the relatively tall POL modules 110-1, 110-2.Lower surfaces 103A of lid 103 may mate with the top surfaces of the POLmodules 110-1, 110-2 and lower surface 103B may mate with the topsurface of the semiconductor die 101. Referring to the side view of thesemiconductor package 100 in FIG. 11, dotted arrows 104, 105 and 106show the direction of heat flow in the package. Heat generated by thesemiconductor die 101 typically flows up through the lid as shown byarrow 106. Other proposed in-package power solutions rely on removal ofthe heat generated in the regulator circuits through the substrate, thusheating the substrate and the semiconductor die. However, the POLmodules 110-1, 110-2, as shown provide thermally conductive conduitsbetween the substrate and the lid, facilitating removal of heatgenerated by the output circuits directly through the lid and furtherprovide a path for heat flow from the die 101 through the substrate 102and up through the POL modules 110-1, 110-2 as shown by arrows 105 and104. As a result, the package 100 provides thermally enhanced operationover other solutions.

III. Semiconductor Package with Bottom-Mounted Integrated POL Module

Referring to FIGS. 15A, 15B, 16A, 16B, 17, and 20, a secondsemiconductor package 300 is shown in bottom and top isometric exploded,top and bottom isometric assembled, and side views, respectively. Likethe package 100 described above (FIGS. 1-3, 10, 11), the secondsemiconductor package 300 includes a multilayer substrate 302 and alarge semiconductor die 301, such as an ASIC, CPU, or GPU, mounted on atop surface 302A of the substrate 302 and also includes a POL module310. However, as shown in FIGS. 15A, 15B, 16A, 16B, and 17, the POLmodule 310 may be mounted on the bottom surface 302B of the substrate302 beneath the die 301 in semiconductor package 300. Although FIGS.15A, 15B, 16A, 16B, and 17 show a single large POL module 310, aplurality of smaller POL modules may be used in place of the singlelarge module shown.

Preferably, the POL module 310 (or POL modules) may occupy substantiallyall of the area beneath the semiconductor die 301 in the same, or a verysimilar, footprint allowing the remaining area, i.e. outside of theprojection of the semiconductor die footprint, on the bottom surface, tobe used for making connections between the substrate 302 and a systemboard. For example, the POL module 310 may preferably be smaller than,and fit completely within the footprint of, the die 301 as shown in theside view of FIG. 17. Note the difference 304 between the edge of thedie 301 (on the top surface 302A of the substrate) and the edge of thePOL module 310 on the bottom 302B of the substrate, which appears inFIG. 17 as symmetrical overhang on the left and right sides of the POLmodule. Although the POL module is shown slightly smaller than the die,it may be the same size as or slightly larger than the die, providedsufficient area remains for making connections between the die and thesystem board.

As shown in FIGS. 15-17, the POL module 310 may be preferably packagedas a leadless module, such as described in the Panel Mold application,having electrical connections for surface mount soldering to respectiveconductive pads on the substrate 302. For example, conductiveterminations, e.g. terminations 315, may be provided along two or moresides of the POL module 310 for surface mount soldering to conductivepads 305 on the bottom 302B of the substrate 302. Additionally,conductive terminations, e.g. terminations 325A may be arranged alongthe top surface 310A of the POL module 310 for surface mount solderingto conductive pads 305 on the bottom 302B of the substrate 302. A pairof the conductive terminations, preferably located centrally and near anedge of the POL module 310 may be provided for making AC powerconnections, e.g. terminals 326A shown in FIG. 15B along a centerlineand close to one edge of the POL module 310. Conductive terminations forthe relatively low power bias and control signals may be provided alongan edge of the module, e.g. terminals 317 are shown formed in an edge ofthe POL module 310 in FIG. 15B.

Preferably the conductive pads 305 on the bottom surface 302B may beelectrically and thermally connected to conductive pads 307 on the topsurface 302A of the substrate 302 (e.g. using conductive vias betweenthe substrate layers (not shown)), which connect with power terminals303 located on the bottom surface 301B of die 301. As shown in FIGS.15A, 15B, and 17, direct vertical alignment may be established betweenpower terminals 303, conductive pads 307, conductive pads 305, andconductive terminations 315 providing the shortest electrical andthermal path between the POL module 310 and the die 301. Additionally,the power terminals 303, conductive pads 307, conductive pads 305, andconductive terminations 315 may be spatially arranged to allow signalconnections to be routed between them on the inner and optionally outerlayers of the substrate 302. For example, the power connectionsincluding terminals 303, pads 307, vias (not shown), pads 305, andterminations 315 and 325A are shown spaced apart and generally arrangedin columns, e.g. five columns are shown in FIGS. 15A, 15B. As shown inFIGS. 15B and 16B, the POL module 310 may include conductive coverings316A, 316B extending over the top 310A and bottom 310B surfaces of thePOL module 310, which as discussed above may enhance the thermal andnoise performance of the POL module 310 and help contain the magneticfields in the transformer cores.

Referring to FIG. 16B, the POL module 310 may optionally includeconductive terminals, 325B, 326B on the bottom surface 310B preferablyaligned with the respective conductive terminations 325A, 326A on thetop surface 310A of the POL module 310. Such through-moduleterminations, described in the Panel Mold application, may enhance thethermal conductivity, providing heat conductors through the POL module310. As described in the Panel Mold application, a conduit (an exampleof which, conduit 265, is shown in FIG. 11 of the Panel Moldapplication) may expose conductive features to provide thermal andelectrical connections between a substrate and the top and/or bottomconductive layers. The conductive terminations 325B, 326B may be used toengage with suitable terminations on the system board, directly orthrough a socket, to provide electrical connections and or allow heat tobe conducted away through the system board as described below inconnection with FIG. 20A.

Remote Gate Driver

Referring to FIG. 19, another power converter system is shown includinga driver 490B, the semiconductor package 300 including the die 301 and aPOL circuit 331 which may include the output transformer 440 andsecondary switches 451-454 of the POL circuit 431 (FIG. 6). Preferably,the driver 490B may include transformer driver circuitry (481, FIG. 9)including switch control circuitry (e.g. 425, FIG. 9), power regulatorcircuitry (482, FIG. 9), and supervisory circuitry (483, FIG. 9) asdescribed above and may be electrically connected to the semiconductorpackage 300 via connections formed by a system PCB (e.g. system board11A or 11B in FIGS. 20A, 20B) on which the driver 490B and semiconductorpackage 300 may be mounted. Preferably, the switch driver (460: FIG. 6)which is shown as part of the POL circuits described above (431: FIG. 6)may be incorporated into the driver 490B (FIG. 19) to further reduce thesize of the POL module 310.

Although counterintuitive because of the high switching frequency andthe parasitic inductances introduced by the system board, the package ofthe driver 490B, the POL module package, and the semiconductor package300, the switch driver may incorporate resonant gate driver techniques(See, e.g. Controller patent: Col. 13, ln 56 -Col. 15, ln 24; FIGS. 8,9) to use the inductances introduced by the connections between theseparated driver 490B and the POL module 310 in semiconductor package300 as some or all of the inductance required to resonantly charge anddischarge the gate capacitances of the secondary switches in therectification circuit of the POL module 310. Preferably additionalinductance may be added in series with gate runs of the gate drivecircuit using discrete, e.g. chip, inductors, to trim the circuit to thedesired resonant frequency. For example, a power converter of the typeshown in FIG. 19 configured to operate at 2 MHz with 250 nS half-cyclesmay require gate-voltage rise and fall times of 60-80 nS. Secondaryswitches configured to deliver 350 to 400 Amperes to the load mayrequire 60 nC of gate charge to turn ON or OFF, representingapproximately 12 nF of gate capacitance on each terminal 446, 449. Thetotal inductance in the driver circuit between gate drivers in thedriver 490B and the secondary switches in the POL module 310 thereforeshould be limited to 7.6 to 13.5 nH. Allowing for 1 nH of packageinductance for each of the driver and POL module and discrete inductanceof approximately 3 nH, the maximum distribution inductance budget forthe gate runs is between 2.6 and 8.5 nH. Design rules may be provided tokeep the gate runs within the allocated inductance budget, e.g. limitingthe length and width of the conductive traces, requiring a ground planein an adjacent layer separated by an acceptable dielectric thickness.

As described above, the controller may detect and adjust for smalltiming errors produced by differences in the parasitic inductances inthe AC power bus 410 and in the gate drive signal bus 415. Preferably,more than 50%, or 75%, or most preferably more than 90% of the energystored in the gate capacitances of the secondary switches in the POLmodule 310 may be recycled using at least in part the inductancesintroduced by the wiring between driver and POL module.

As shown in FIG. 19, the control outputs 426, 429 of driver 490B (e.g.either bias and control or gate driver outputs) may be connected to asignal bus 415 on the system board which may in turn be connected toterminals 465, 466 on the substrate 302 of the package 300 and carriedthrough the substrate 302 to input terminals 449, 446, respectively.Similarly, a communication bus 497 as described above in connection withFIG. 9 may provide communication between the semiconductor package 300,e.g. with the die 301, and supervisory circuitry in the driver 490B.

The AC power connections 410 between the driver 490B (outputs 427, 428)and the POL module 310 (AC Inputs 447, 448) may be provided in part bythe substrate 302 in the manner described above in connection with FIG.4 using suitable conductor free zones around the AC connections formedin the substrate. Providing connections between the POL module 310 andthe driver 490B through the substrate 302 may require routing the ACpower laterally in or on the substrate in turn requiring elimination ofany conductive features in a volume surrounding the AC power conductors,e.g. in a space radially around the conductors including a number ofadjacent layers above and below the layer in which the AC powerconnections are made. Alternatively, the AC power connections 410 may beestablished between the system board (e.g. system board 11A, FIG. 20A)and the POL module 310 directly, e.g. using a socket 15 with suitableconductive terminations 16B to engage with terminations 326B on thebottom surface 310B of the POL module 310.

Alternatively, the AC power connections 410 between the system board andthe POL module 310 may be formed using a wire harness 18 including aconnector body configured to engage with AC power pins 327 preferablyprotruding from the bottom surface 310B of the POL module as shown inFIG. 18. The AC power pins 327 may be configured to be inserted into,engage with, and soldered to conductive features, e.g. plated holes,formed in the POL module 310. For example, a conduit, such as thefeature 265 shown in FIG. 11 of the Panel Mold application, may beappropriately shaped and sized to provide a conductive receptacle for aconductive pin.

Underside Thermal Management

Referring to the side view of FIG. 20A, the package 300 may be assembledonto a surface of system board 11A using a socket 15 which may includecontacts 16 for establishing electrical connections to the bottomsurface 302B of the substrate. Heat may be conducted from the POL module310 up through the substrate 302, e.g. through conductive features, 305,307 and the connections there between, up through, and out the top of,the die 301, into a heat sink or lid (not shown) as represented by arrow21 in FIG. 20A. Optionally, heat may be conducted away from the POLmodule through the system board 11A as represented by arrows 23 in FIG.20A.

Referring to the side view of FIG. 20B, the package 300 may be assembledonto a surface of system board 11B using a low profile socket 15B havingan aperture sized to accommodate the POL module 310 and contacts 16 forestablishing electrical connections to the bottom surface 302B of thesubstrate. However, the system board 11B may include an aperture 17sized to accommodate the POL module 310, providing a lower profilemounting alternative. In the embodiment of FIG. 20B, heat may be removedfrom the POL module 310 through the aperture 17 as represented by arrow22, e.g. using forced air convection, a heat sink, or a cold plate (notshown).

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, a single resonant capacitor may be used instead of the tworesonant capacitors shown in the symmetrical balanced circuit of FIG. 5and FIG. 6. A center-tapped secondary circuit may be used in place ofthe full-bridge circuit shown. Although full-bridge driver circuits areshown in FIGS. 5, 6, and 9, a half-bridge primary circuit may be used todrive the power transformer. Although converter topologies having one,and two POL circuits have been shown, it will be appreciated that alarger number of POL circuits may be used. The POL outputs may beconnected in parallel as shown to supply higher current loads, orindependently for multiple loads. The POL circuits may be deployedwithin the semiconductor package or at locations near, or adjacent tothe semiconductor package or other loads. The magnetically permeablefluid injected into the apertures 155 of the PCB 151 can include apowder with or without a curable medium. There can be two or moresemiconductor chips mounted on the substrate 102, in which thesemiconductor chips are all powered by the POL modules 110. Themagnetically permeable fluid can be a liquid material.

Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A method of supplying power received from aninput source at an input voltage to circuitry on one or moresemiconductor chips mounted in or on a semiconductor package at a DCoutput voltage, comprising: providing a driver circuit for deploymentoutside or off the semiconductor package having an input for receivingpower from the source, circuitry adapted to drive a transformer, and adriver output; providing one or more output circuits for deployment inor on the semiconductor package, each output circuit including a printedcircuit board, a power transformer including a first winding and asecond winding, an input connected to the first winding for receiving ACpower from the driver output, a rectification circuit connected to thesecond winding for rectifying power received from the transformer, andan output connected to the rectification circuit for supplying DC powerto the one or more semiconductor chips; providing a power bus forcarrying AC power from the driver output to the input of each of the oneor more output circuits in the semiconductor package; operating thedriver circuit to drive the transformer in a series of converteroperating cycles, each converter operating cycle characterized by twopower transfer phases of essentially equal duration during which one ormore switches in the driver circuit are ON and power is transferred fromthe input to the output via the transformer; and deploying the drivercircuit at a first location outside or off of the semiconductor package;wherein power is supplied to the semiconductor package by the drivercircuit at a bus voltage that is a multiple, X, times greater than aload voltage required by the one or more semiconductor chips.
 2. Themethod of claim 1 wherein the semiconductor package includes a packagesubstrate on which the one or more semiconductor chips are mounted; andthe providing the power bus further comprises providing a high voltageconnection through the package substrate, the high voltage connectionincluding a volume in the package substrate defined by a projectionaround the high voltage connection that is free of conductive features.3. The method of claim 1 further comprising: forming a resonant circuitincluding a winding of the transformer, the resonant circuit beingcharacterized by a characteristic resonant period; and wherein operatingthe driver circuit further comprises providing power during powertransfer intervals, and each power transfer interval has a duration lessthan the characteristic resonant period.
 4. The method of claim 3further comprising: providing at least one resonant capacitorelectrically connected to the power bus.
 5. The method of claim 4further comprising: providing a clamp switch configured to clamp theresonant capacitor; and wherein each power transfer interval comprisesfirst and second resonant intervals, each having a duration less thanthe characteristic resonant period, during which a resonant currentflows through a winding of the transformer at the characteristicresonant frequency; and wherein the converter operating cycles furthercomprise a clamp interval occurring after the first resonant intervaland before the second resonant interval and having a clamp durationduring which the clamp switch is ON and provides a low impedance shuntacross the resonant capacitor.
 6. The method of claim 5 furthercomprising adjusting the clamp duration as a function of power deliveredto the one or more semiconductor chips.
 7. The method of claim 6 furthercomprising reducing the clamp duration in response to a decrease in thepower delivered to the one or more semiconductor chips.
 8. The method ofclaim 5 further comprising detecting a resonant current at the end of aselected one or more of the first or second resonant intervals andadjusting the timing of the converter operating cycles.
 9. The method ofclaim 1 further comprising: providing a bias power output in the drivercircuit for supplying power to operate circuitry in the one or moreoutput circuits.
 10. The method of claim 1 further comprising: providinga control output in the driver circuit; providing a control circuit inthe one or more output circuits, sending control signals from the drivercircuit to the one or more output circuits; and synchronizing operationof the one or more output circuits using the control signals.
 11. Themethod of claim 1 wherein: the semiconductor package includes a packagesubstrate; the one or more semiconductor chips comprise a singlevery-large-scale-integrated (“VLSI”) semiconductor die mounted to thepackage substrate; the one or more output circuits comprise a first anda second output circuit, each mounted to the package substrate adjacentto the VLSI semiconductor die; and the power bus further comprises afirst and a second high voltage connection, each including avertical-extension through the package substrate located adjacent to arespective one of the first and the second output circuits andterminating on a top surface of the package substrate in a padpositioned to align with a respective input terminal of the respectiveoutput circuit and terminating on a bottom surface of the packagesubstrate in an interface connection, and including a respectiveconductor-free volume in the package substrate defined by a projectionaround the respective the vertical extension that is free of conductivefeatures.
 12. The method of claim 11 further comprising providing thepackage substrate with an inter-layer breakdown voltage that is lowerthan the bus voltage.
 13. The method of claim 11 further comprising:providing the power transformer with a step down ratio, N, equal to K;and connecting the outputs of the one or more output circuits inparallel.
 14. The method of claim 11 further comprising: providing thepower transformer with a step down ratio, N, that is less than K; andconnecting the inputs of the one or more output circuits in series. 15.The method of claim 1 further comprising: providing a regulation stagein the driver adapted to control the output voltage of the driveroutput.
 16. The method of claim 15 further comprising: receiving acontrol signal from the one or more semiconductor chips for adjustmentof the DC output voltage; adjusting the output voltage of the driveroutput in response to the received control signal.
 17. The method ofclaim 1 wherein X is greater than or equal to
 10. 18. The method ofclaim 1 wherein X is greater than or equal to
 20. 19. The method ofclaim 1 wherein X is greater than or equal to
 40. 20. The method ofclaim 1 wherein the rectification circuit comprises a first seriescircuit having a first switch and a second switch, the first switchbeing connected to the second switch at a first junction, the firstseries circuit having two end terminals that are connected to the outputof the output circuit, and the first junction being connected to a firstterminal of the second winding of the power transformer.
 21. The methodof claim 20 wherein the rectification circuit further comprises a secondseries circuit having a third switch and a fourth switch, the thirdswitch being connected to the fourth switch at a second junction, thesecond series circuit having two end terminals that are connected to theoutput of the output circuit, and the second junction being connected toa second terminal of the second winding of the power transformer. 22.The method of claim 1 wherein the one or more semiconductor chipsfurther comprises a processor core.
 23. The method of claim 1 whereinthe driver circuit comprises a plurality of primary switches to drivethe first winding of the power transformer, and a resonant current flowsin the first winding during the power transfer phases, and the methodcomprises turning one or more of the primary switches OFF essentially attimes when the resonant current returns to zero.
 24. The method of claim23 wherein a magnetizing current flows through the primary windingduring the power transfer phases, and each converter operating cyclecomprises a plurality of energy-recycling intervals during which atleast one primary switch transitions to OFF, and the method comprisesusing the magnetizing current to charge and discharge capacitancesduring the energy-recycling intervals.
 25. The method of claim 1 furthercomprising: providing a second driver circuit for deployment outside oroff the semiconductor package having an input for receiving power fromthe source, circuitry adapted to drive a transformer, and a seconddriver output; providing one or more additional output circuits fordeployment in or on the semiconductor package, each additional outputcircuit including a printed circuit board, a power transformer includinga first winding and a second winding, an input connected to the firstwinding for receiving AC power from the second driver output, arectification circuit connected to the second winding for rectifyingpower received from the transformer, and a second output connected tothe rectification circuit for supplying DC power to the one or moresemiconductor chips at a second load voltage; providing a second powerbus for carrying AC power from the second driver output to the input ofeach of the one or more additional output circuits in the semiconductorpackage; operating the second driver circuit to drive the transformer ina series of converter operating cycles, each converter operating cyclecharacterized by two power transfer phases of essentially equal durationduring which one or more switches in the driver circuit are ON and poweris transferred from the input to the output via the transformer; anddeploying the second driver circuit as a self-contained unit at a secondlocation outside or off of the semiconductor package; wherein power issupplied to the semiconductor package by the second driver circuit at abus voltage that is a multiple, X, times greater than the second loadvoltage required by the one or more semiconductor chips.
 26. The methodof claim 1 further comprising establishing X as an integer.
 27. Themethod of claim 1 further comprising establishing X as a non-integerrational number.
 28. The method of claim 1 further comprising deployingthe driver circuit as a self-contained unit at the first location. 29.The method of claim 1, further comprising detecting a resonant currentat the end of a selected one of the power transfer phases and adjustingthe timing of the converter operating cycles.
 30. The method of claim 1further comprising: providing a switch driver output in the drivercircuit; providing a control input connected to one or more secondaryswitches in the rectification circuit, using the switch driver output toresonantly charge and discharge capacitances associated with the controlinput to operate the one or more switches in the rectification circuit.31. The method of claim 1 wherein: the semiconductor package includes apackage substrate; the one or more semiconductor chips comprise a singlevery-large-scale-integrated (“VLSI”) semiconductor die mounted to thepackage substrate; and the one or more output circuits comprise apoint-of-load (POL) module mounted to the package substrate beneath theVLSI semiconductor die.
 32. The method of claim 31 wherein: the powerbus further comprises a first and a second high voltage connection, eachincluding an extension laterally along the package substrate terminatingon a bottom surface of the package substrate in a pad positioned toalign with a respective input terminal of the POL module and terminatingin an interface connection, and including a respective conductor-freevolume in the package substrate defined by a projection around therespective the extension that is free of conductive features.
 33. Themethod of claim 31 further comprising: providing a conductive terminalextending from a surface of the POL module electrically connected to theinput of the output circuit; providing a connector adapted to mate withthe conductive terminal; wherein the power bus further comprises theconnector and the conductive terminal.
 34. The method of claim 32further comprising: providing a switch driver output in the drivercircuit; providing a control input connected to one or more secondaryswitches in the rectification circuit, using the switch driver output toresonantly charge and discharge capacitances associated with the controlinput to operate the one or more switches in the rectification circuit.35. The method of claim 30 further comprising: providing a discreteinductor in series between the switch driver output and the controlinput.
 36. The method of claim 31 wherein the POL module furthercomprises a conductive shield on one or more outer surfaces of the POLmodule.
 37. The method of claim 1 wherein: the semiconductor packageincludes a package substrate; the one or more semiconductor chipscomprise a single very-large-scale-integrated (“VLSI”) semiconductor diemounted to the package substrate; the one or more output circuitscomprise a first, a second, a third and a fourth output circuit, eachmounted to the package substrate adjacent to the VLSI semiconductor die;and the power bus further comprises a first and a second high voltageconnection, each including a vertical-extension through the packagesubstrate located adjacent to a respective one of the output circuitsand terminating on a top surface of the package substrate in a padpositioned to align with a respective input terminal of the respectiveoutput circuit and terminating on a bottom surface of the packagesubstrate in an interface connection, and including a respectiveconductor-free volume in the package substrate defined by a projectionaround the respective the vertical extension that is free of conductivefeatures.
 38. An apparatus comprising: a semiconductor package includinga substrate having a plurality of interface connections connected to atleast one surface of the package substrate and one or more semiconductorchips mounted to the substrate, the interface connections adapted forelectrical connection to a system board; one or more output circuitshoused in the semiconductor package, each output circuit including aprinted circuit board, a power transformer including a first winding anda second winding, an input connected to the first winding for receivingAC power, a rectification circuit connected to the second winding forrectifying power received from the transformer, and an output connectedto the rectification circuit for supplying DC power to the one or moresemiconductor chips; and a power bus connected to selected interfaceconnections for carrying AC power at a bus voltage from the system boardto the input of each of the one or more output circuits in thesemiconductor package; wherein the bus voltage is a multiple, X, timesgreater than a voltage required by the one or more semiconductor chips.39. The apparatus of claim 38 further comprising: a driver circuitlocated outside the semiconductor package having an input for receivingpower from a source, circuitry adapted to drive the transformer, and adriver output for supplying AC power to the transformer via the powerbus; and the driver circuit including a controller configured to drivethe transformer in a series of converter operating cycles, eachconverter operating cycle characterized by two power transfer phases ofessentially equal duration during which one or more switches in thedriver circuit are ON and power is transferred from the input of thedriver circuit to the output of the one or more output circuits via therespective transformer of the one or more output circuits.
 40. Theapparatus of claim 38 wherein the power bus further comprises a highvoltage connection extending vertically through the package substrateand having a volume in the package substrate defined by a projectionaround the high voltage connection that is free of conductive features.41. The apparatus of claim 39 further comprising a resonant circuitincluding a winding of the transformer, the resonant circuit beingcharacterized by a characteristic resonant period; and wherein eachpower transfer phase includes a duration that is less than thecharacteristic resonant period.
 42. The apparatus of claim 40 furthercomprising at least one resonant capacitor electrically connected inseries with the first winding.
 43. The apparatus of claim 39 wherein thedriver circuit further comprises a bias power output for supplying powerto operate circuitry in the one or more output circuits.
 44. Theapparatus of claim 39 wherein: the driver circuit further comprises acontrol output for sending a control signal to the one or more outputcircuits; the one or more output circuits further comprise a controlcircuit adapted to synchronize operation of the one or more outputcircuits using the control signals.
 45. The apparatus of claim 38wherein: the one or more semiconductor chips comprise a singlevery-large-scale-integrated (“VLSI”) semiconductor die; the one or moreoutput circuits comprise a first and a second output circuit, eachmounted to the package substrate adjacent to the VLSI semiconductor die;and the power bus further comprises a first and a second high voltageconnection, each including a vertical-extension through the packagesubstrate located adjacent to a respective one of the first and thesecond output circuits and terminating on a top surface of the packagesubstrate in a pad positioned to align with a respective input terminalof the respective output circuit and terminating on a bottom surface ofthe package substrate in an interface connection, and including arespective conductor-free volume in the package substrate defined by aprojection around the respective vertical extension that is free ofconductive features.
 46. The apparatus of claim 38 wherein the packagesubstrate has an inter-layer breakdown voltage that is lower than thebus voltage.
 47. The apparatus of claim 38 wherein the power transformercomprises a step down ration, N, equal to X; and the outputs of the oneor more output circuits are connected in parallel.
 48. The apparatus ofclaim 38 wherein the power transformer comprises a step down ration, N,that is less than X; and the inputs of the one or more output circuitsare connected in series.
 49. The apparatus of claim 39 wherein thedriver circuit further comprises a regulation stage adapted to controlthe output voltage of the driver output.
 50. The apparatus of claim 49wherein the driver circuit is connected to receive a control signal fromthe one or more semiconductor chips and is adapted to adjust the outputvoltage of the driver output in response to the control signal.
 51. Theapparatus of claim 38 wherein X is greater than or equal to
 10. 52. Theapparatus of claim 38 wherein X is greater than or equal to
 20. 53. Theapparatus of claim 38 wherein X is greater than or equal to
 40. 54. Theapparatus of claim 38 wherein the rectification circuit comprises afull-bridge configuration.
 55. The apparatus of claim 38 wherein thesecond winding comprises a center-tap and the rectification circuitcomprises a center-tap configuration.
 56. The apparatus of claim 38wherein the one or more semiconductor chips comprise a processor core.57. The apparatus of claim 38 wherein the rectification circuit furthercomprises one or more secondary switches and a control circuit adaptedto turn the one or more secondary switches OFF essentially at times whena current in the second winding returns to zero.
 58. The apparatus ofclaim 39, wherein the driver circuit comprises a plurality of primaryswitches to drive the first winding of the power transformer, a resonantcurrent flows in the first winding during the power transfer phases, andthe driver circuit comprises a control circuit configured to turn one ormore of the primary switches OFF essentially at times when the resonantcurrent returns to zero.
 59. The apparatus of claim 38 in which X is aninteger.
 60. The apparatus of claim 38 in which X is a non-integerrational number.
 61. The apparatus of claim 39 in which the drivercircuit comprises compensation circuitry to detect and adjust foreffects of at least one of parasitic capacitances or inductancesintroduced by separation of the driver circuit and the one or moreoutput circuits.
 62. The apparatus of claim 61 further comprisingcircuitry configured to detect a resonant current at the end of aselected one or more of the power transfer phases and adjust timing ofthe converter operating cycles.
 63. The apparatus of claim 38,comprising the system board.
 64. The apparatus of claim 38 in which theinterface connections comprise at least one of connector pins, ball gridarray, or land grid array.